Power Supplies, the next step in superb sound

Introduction

The technical story behind this power supply design and how it came to this version, is described in its own section (Circuit: step-by-step). Right here, I like to give some background to how I came to this particular design. Before I do see (next to the two pictures below, I still want to show (again) the circuit. Every one who knows a little bit from standard electronics, will say immediately "Well, what's the big deal about THIS power supply?" Actually a very valid question. I did that as well when I first saw it. Even though it was the very early version which is a bit different from the final version. Honestly, this is like any simple standard power supply you can find in electronic leaning books. At least the principle... I guess in the end of the day it is indeed about this simplicity. We need a stable power supply for the DAC (specially the good old DDDAC1543), so low output impedance and good filtering is needed. Well, this power supply does all that.... and it does it very well. Make it more complex (very easy....) and too many things might get in the way. I tried this.... Switching power supplies, highly regulated power supplies, LAB power supplies and so on. They all did not clearly sound as good as this (simple) one! And that is all what counts....

Below is the circuit we discuss. The technical description is the circuit section. Thought it was good to show it again here as well
This circuit is part of the DDDAC1794 documentation which you can download from the download section or push the button below:

How it all started... Actually it started because Reinhard (and Klaus as well) was using the 120 Chips DDDAC1543, which consumes awesome 7A at 12 Volt. Hard to run with batteries and also hard to find a good power supply. So they asked Bernd, as he made good experience in the past with his hand made power supplies for amplifiers. He hand picked parts and fine tuned the design by many listening sessions... So he made this high power 12 Volt version and when being tested, we all went like "wow!" this is so good, how come we never tried this before? Well now we did and now we have it... Of course Bernd promised me a hand made board as well, so I could build my version for my DDDAC1543, which is "only a 60 chip".... The result is still very hand made on for my purposes only. You see the result at the left. I used good filtering and a heavy metal toroid transformer. Also in this case the audible result was awesome, hence I said to myself: "Whenever you are ready with the DDDAC1794, it must have this kind of power supply"

The DDDAC1543 Power Supply: How it all started: The handmade design from Bernd. Actually so flexible, it can be used up to 80Volts and 10A.

Designing the DDDAC 1794 version (Prototypes)

This is worth a few lines at its own. As said, I used the Basic (high power) design from Bernd as a start. I wanted the DDDAC1794 power supply to be simple to build and as it should be used in an enclosed chassis, I did not want all kind of extra electronics monitoring output current, overload etc. This basically reduced the power supply to a Transformer with Rectifier, Filter, control element and errors amplifier (see tech section...) But I wanted to be sure that the power supply was extraordinary good in noise and ripple rejection. Why? A DAC is not an analog amplifier. There is much more issue with high frequency interference as with a 20kHz bandwidth analog device. So I was looking for lowest possible noise on top of the already low output impedance. Before doing anything, I just wanted to make sure I fully understood, what the Bernd power supply was actually doing in terms of high bandwidth behaviour. From that I wanted to do several simulations and see how I could improve the noise rejection of the circuit. I already noticed in an early stage, that Bernd's power supply had a couple of delay times in the error amplifier, making it very smooth for analog power supply, but there might be something to gain here next to making it simple

Enough considerations. Next to my ears (most of the readers now that) I also like to measure and simulate to finally converge to optimum results. Now building a power supply and measuring with an analyzer and trying ten, twenty different configurations, with multiple values of components is just an impossible task. For that I have the program TINA, which is a spice kind of simulator electronics program, but for DIY very affordable. I spent literally weeks with the power supply, because every time you want sleep over things you tried. What I did was trying all kind of values of capacitors, RC filters, extra gain, HF shortcuts, different current through the transistors and lost more....

Basically this sound like simple trial and error, which is not. You quickly understand from the results, what is actually happening in the circuit. By that you can try new values or configurations. My main finding was, that the error amplifier needed a clean voltage source, the LED for the error amplifier need its source from the regulated output and the amplifier needs an HF shortcut from the output. On top, no RC elements in the error amplifier. Than by adding a large output capacitors the output is smooth as a baby :-)

Before...

And after the modifications

The prototype DDDAC1794 result So I designed two prototypes, one with one TIP122 section for max 1A output and a double TIP122 section for 2A. In fact the TIP122 can bear much more, but things get difficult with heatsinks on the printed circuit board. For both 5Volt and 12Volt, the 1A version delivers enough headroom for both a 4-Deck version of the DAC (12 Volt) or for the WaveIO module (5 Volt). As this power supply is not so easy to built for every not so advanced DIY without the use of a PCB, I now offer this as a KIT. Check the sales site 1794...

The DDDAC1794 Power Supply (Prototypes): What eventually came out of it, fine tuned for the DDDAC1794 NOS DAC. The top one is 5-12Volt max 1A. The bottom one up to 2A. I will make the 1A one available as kit.

The design is quite universal and can be used for many other voltages and power ranges. Keep in mind it needs roughly 6 Volts more input than output... within some reasonable ranges it is just a matter of size of the transformer and heat sinks. Warning: there is NO overload or short circuit protection. Nor is there a thermal protection. For safety there is a fuse and that's it. All under the motto, less is better ;-) A little care with the handling of this supply is therefore needed. Most important, it sounds really great!

The final DDDAC Power Supply version As announced, I reworked my own prototypes into an easy design for both 5 Volt and 12 Volt. The maximum current is roughly 1A, which is more than enough. I tried it my self and with 1A the heatsink gets quite warm, but nothing to worry about. Under normal DDDAC conditions, things are very nicely balanced. The only difference between the 5 volt and 12 Volt version is the AC voltage of the transformer. In the 5 Volt kit there is a 9Vac transformer and for the 12 Volt kit a 15Vac version is supplied. Both 25VA, so things stay cool :-) Last but not least the kit can be used for 230Vac mains as well 115Vac mains. Just make sure to put the right jump wires in place... click here for a detailed image ...

The DDDAC Power Supply: The final version: The PCB is the same for both versions. Just the toroidal Transformers are different

Top view... A few final words; the design is quite universal and can be used for many other voltages and power ranges. Keep in mind it needs roughly 6 Volts more input than output... within some reasonable ranges it is just a matter of size of the transformer and heat sinks. Warning: there is NO overload or short circuit protection. Nor is there a thermal protection. For safety there is a fuse and that's it. All under the motto, less is better ;-) A little care with the handling of this supply is therefore needed. Most important, it sounds really great!

The DDDAC Power Supply: For both versions the trimmer MUST be set first to 5V or 12V...

Important: --->

Before the power supply is attached to any of the boards, make sure to set the trimmer for 5V or 12V!

Keep reading ...... the story continuous with the analog output ( output options )